This invention relates generally to fluid-irrigated, ultrasonically-operated cutting devices, and particularly to surgical instruments of the type which employ ultrasonic energy for operating on tissue. This invention especially relates to an ultrasonic decoupling sleeve interposed in a fluid passage to improve the operating characteristics of a surgical device in a surgical irrigation-aspiration apparatus, such as is used in eye surgery.
Surgical instruments utilizing ultrasonic vibrations in combination with the circulation of irrigation liquid over the operative site for the removal of tissue from a biological body are well known and widely used, particularly in enclosed and substantially enclosed operative sites. Such surgical instruments are particularly well adapted for the removal of cataracts and other surgical procedures perfomred on the eye. Ultrasonic surgical instruments of the type with which the present invention is primarily concerned conventionally employ an elongated probe or operative tip having an end rigidly attached through a vibration transmissive member to a transducer for supplying ultrasonic energy to the other or free end of the probe. The ultrasonic energy is emitted to dislodge and break-up or emulsify tissue from the oeprative site for removal by aspiration. Irrigating fluid is delivered through a shield, or sheath, surrounding the body of the probe for discharge adjacent to the tip or free end of the probe and is returned by suction through a hollow center of the tubular body of the probe. An ultrasonic surgical aspirator of this type is shown in U.S. Pat. No. 3,805,787 as including conduits for applying suction through the center of the vibration transmitting operative probe and for supplying irrigating fluid around the outer surface of the probe through a passage defined by a tubular shield. The irrigation fluid flows around the free end of the probe element and back through the center of the prove to effectively irrigate and remove discharged and emulsified tissue. Various shield arrangements for controlling or directing the flow of irrigating fluid in the vicinity of the free end of the operative probe are shown in that prior patent, as well as in U.S. Pat. Nos. 3,693,316 and 4,515,583.
Significant attention in the art for improving the operative characteristics of those devices for the convenience of the surgeon and to enhance the efficacy of the instrument for the safety of the patient has been directed to solving a number of problems. For example, it has been proposed to form the ultrasonic rigid tip cap sleeve in one piece, or as a transparent member and to provide devices which can accommodate increasingly smaller incisions. Such sleeve components defining the irrigation fluid conduit passages of those instruments have, however, sometimes channeled cavitation bubbles caused by the ultrasonically-vibrating member and as a result of directing the irrigating fluid around the ultrasonic tip. Those caviation bubbles create a visual obstruction in delicate surgery, and an annoyance in the eye during surgery. Usually the surgeon is required to interrupt the surgery to permit the aspiration system to remove the bubbles before resuming the surgery.
Such cavitation and bubbles may also adversely affect the stability of the ultrasonic action during surgery. For example, it is a consistent desire in the production of such instruments to provide power consistently to the ultrasonically vibrated tip without power fall-offs or surges so that the surgeon can expect the ultrasonic power delivered by the tip during the surgical procedure to be conveniently consistent and thus minimize his attention to fluctuations and variations in the operative characteristics of the instrument. It is believed that the presence of such cavitation bubbles has an effect on the stability of the instrument in creating variations in the mechanical impedance in the instrument which causes corresponding variations in the mechanical operating characteristics of the instrument. Accordingly, it is desired to decouple and isolate the operative tip from the outer shell and to avoid cavitation bubbles in the fluidic path in order to preclude power drop-off and reduce instability in the operative characteristics of the instrument.
It is thus a general object of this invention to improve an instrument of the type described by improving its stability and by reducing or eliminating cavitation of and bubble formation in the irrigating fluid.
It is also a general aim in the art to improve load isolation, acoustical and hydraulic pressure confinement, and to achieve sound reduction and load stabilization in connection with such instruments.